The disclosure is based on a brake application system for vehicles, particularly for rail vehicles, containing a wear adjuster constructed as a brake rod or thrust rod actuator and having a screw drive which has a threaded spindle and a nut to be screwed to the threaded spindle, as the screw parts.
A brake application system of this type is known from European Patent Document EP 0 699 846 A2. A wear adjuster for rail vehicle brakes in the form of brake rod and thrust rod actuators which, in the case of a brake pad and brake disc wear respectively, keep the brake pad play constant. This takes place by a change of length of the screw drive, in the case of thrust rod actuators, an increasing actuator length causing a reduction of the brake pad play. The drive of the known screw drive takes place mechanically by a brake linkage with a thrust rod which, in the event of an excess stroke of a brake actuator constructed as a pneumatic cylinder-piston driving gear, is operated by a rocker lever.
In the present disclosed system, at least one of the screw parts is electrically driven for the wear adjustment.
As a result of the direct electric control of at least one of the screw parts of the screw drive for the wear adjustment, the known brake linkage can be eliminated. Since the electric drive unit has a smaller size than the brake linkage, space and weight are saved. Furthermore, as a result of the electric control of the screw drive, a more precise adjusting becomes possible in comparison to a mechanical operation.
According to the present system, an electric drive unit is provided which consists of an electric motor with a gearing arranged on the output side. The gearing output is rotationally coupled with an electrically driven screw part. The electric motor may be a d.c. motor. The gearing contains a planetary gear axially adjoining the electric motor as well as one or more gearwheel stages arranged behind this planetary gearing.
A clutch by which the electrically driven screw part, in the event of the presence of an axial force originating from a braking, can be non-rotatably coupled with a non-rotatable part, for example, a housing, and otherwise can be uncoupled therefrom. As a result, the screw part loaded by the caliper levers of the brake application system by the braking power is supported on the housing and not on the electric drive unit. Thus, the electric drive unit can be smaller, which also contributes to a reduction of the size.
A slip clutch may be arranged between the electric drive unit and the electrically driven screw part. The slip clutch is constructed to slip when stop positions are reached and is otherwise coupling. One stop position is formed, for example, by the application of the brake pads on the brake disc. Another stop position is formed by a screw connection end position in which the electrically driven screw part is screwed to the stop into the other screw part or vice-versa. In the latter case, the electrically driven screw part would be rotated along with the other screw part, and the rotating movement would be undesirably transmitted to the electric drive unit. The slip clutch therefore protects the electric drive unit from impacts when the stop positions are reached in that it slips in order to permit the motor to softly and gradually conclude its rotating movement and uncouples it from torques introduced by other components. The slip clutch is preferably connected between the coupling and the electric drive unit.
The other screw part of the screw drive can be rotatably driven for the emergency and/or auxiliary release of the brake. The screw drive is then used in the sense of a combination of functions in a constructional unit, on the one hand, for the wear adjustment and, on the other hand, for the emergency and/or auxiliary release of the brake, whereby space and weight can again be saved.
These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings.